Forced Circulation Research Articles

The preliminary design of emergency core cooling scheme and loss-of-coolant accident analysis for Tsinghua high flux reactor

This paper proposes the preliminary emergency core cooling scheme for Tsinghua High Flux Reactor. According to the thermohydraulic characteristics of high flux reactors, forced circulation needs to be maintained by emergency pumps in the early stage. When the decay power is low enough, natural circulation between core and the reactor pool is initiated to remove the residual core heat. The sources of safety injection are accumulators and reactor pool. Accumulator injection can ensure core safety in the early stage and reactor pool injection can maintain long time stable forced circulation. To avoid emptying the reactor pool, the waterproof zone needs to be built. The waterproof zone consists of reactor pool and several finite volume dry pools. All pipelines and equipment in the reactor coolant system are placed in the dry pools. Once break accident occurs, the dry pool where the break is located can collect the leaked coolant. With the increase of break back pressure, the break flow is restricted. The current scheme is modeled by Relap5 and different size breaks at four locations (namely core inlet, core outlet, primary heat exchanger inlet and main pump inlet) are assumed. According to the response characteristics of the scheme, the accident process can be divided into five stages: non-shutdown stage, high-injection stage, low-injection stage, stable forced circulation stage and natural circulation stage. Critical heat flux predicted by Sudo CHF correlations is adopted as the primary safety criterion. Through analysis, a success path is found to maintain core safety for a wide range of loss-of-coolant accident scenarios.

Exploring Cynara cardunculus L. by-products potential: Antioxidant and antimicrobial properties

Cynara cardunculus L. (cardoon), a perennial crop indigenous to the Mediterranean region, has gained recognition for its remarkable resilience to diverse weather conditions and its multifaceted applications across various industries, which includes the use of the flower as a vegetable rennet to produce some cheeses, as a source of biomass for energy, or its seed oil for human consumption, biodiesel, and animal feed. In some applications (e.g. biomass or seed production), when crop is harvested at the end of the growth cycle, the leaves remain as the main by-products, along with the flowers. In the context of a circular economy, the aim of this work was to undergone studies to determinate their biological properties (antioxidant and antimicrobial). Methanolic and ethanolic extracts of C. cardunculus L. (globe artichoke var. scolymus (L.) Fiori) and cultivated cardoon (var. altilis DC.)) leaves and flowers were characterised in terms of their polyphenol profile (total phenolic content (TPC), total flavonoid compounds (TFC), and ultra-high performance liquid chromatography coupled with time-of-flight mass spectrometry (UHPLC-ToF-MS)), antioxidant capacity (free radical DPPH inhibition system, β-carotene bleaching assay), and antimicrobial capacity (minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), antifungal). In addition, the cultivated cardoon leaves extracts were assessed before and after they were dried in an oven with forced air circulation to evaluate if this treatment affected their bioactive profile. Chlorogenic acid, apigenin, and luteolin were the most quantified of a total of sixteen compounds identified by UHPLC-ToF-MS. Cultivated cardoon dry leaf extract presented the best antioxidant capacity for both methanolic (EC50 = 0.8 mg/mL, antioxidant activity coefficient (AAC) = 279.67) and ethanolic (EC50 = 2.1 mg/mL, AAC = 448.06) extracts, compared to the cardoon flower extracts and the globe artichoke leaf extracts. Dried cultivated cardoon leaf extracts presented higher antioxidant capacity than fresh cultivated cardoon leaf extracts, but a greater number of polyphenolic compounds were identified in fresh cultivated cardoon leaf extract. The Gram-positive bacteria were more sensitive to the activity of both ethanolic and methanolic extracts than the Gram-negative and cultivated cardoon dry leaf ethanolic extract presented lower MIC and MBC values (125–2000 µg/mL) for most of the tested microorganisms, thus showing higher antimicrobial activity. As for the cultivated cardoon leaf extracts, the dried leaf extracts exhibited better antimicrobial activity, with lower MIC values, than the fresh leaf extracts. The extracts only demonstrated a slight inhibition against the fungi Aspergillus fumigatus. In conclusion, studies performed indicate that dried leaves maintain their biological activities compared to fresh leaves, and that flowers present significant biological activity which suggests the great potential of the by-products of this crop as a source of active compounds in different industrial applications (e.g. food industry).

Scale effects on core design, fuel costs, and spent fuel volume of pressurized water reactors

The desire to improve the economic competitiveness and deployment pace of nuclear energy through modularization, manufacturing, and series production had led to the development of smaller size reactors. As the standard 17x17 fuel technology is mainly maintained in the pressurized water reactors (PWRs) category, this translates into a lower number of fuel assemblies in the core and sometimes a reduced fuel height. To assess the impact of such scale change in core design on fuel cycle cost and spent fuel volume, a scoping analysis tool is developed based on infinite lattice calculations, leakage, fuel management reduced models, and levelized unit cost of electricity (LCOE) estimate. As such, cost dynamics driven by fuel specific power, burnup, core leakage, feed, cycle length, fuel assembly height as well as uranium market data are captured with consistent set of assumptions and analysis methods. A selection of 5 reactor designs representative of leading PWR developers is assessed and compared. Pursuing higher specific powers and optimal burnups are highlighted as the main fuel cost reduction drivers, nevertheless, practical limitations and opportunities must be evaluated to establish the feasibility of such enhanced fuel operation. In consequence, a detailed core design is performed using SIMULATE3 code for 5 PWR variations including natural and forced coolant circulation modes, two reactor scales, power densities of 73, 112, and 123 kW/l and higher discharge burnups. Design and optimization are performed at the lattice level, for the reflector, and at the core loading level. Satisfactory steady-state operation including power distribution, coolant operating limits, and reactivity requirements are analyzed and reported in this paper. The fuel economics of the detailed core designs confirm the scoping analysis findings. Despite the unlocked power uprates in small PWRs, the achievable burnup for a given fuel specific power requires more enrichment and shorter fuel height results in higher fabrication costs per mass of fuel, which makes scaling down core size a more expensive endeavor on the fuel cycle front. Spent fuel volumes are reported for the PWRs designed in this paper. These volumes are driven by the core average discharge burnup regardless of the scale in consideration. Additional cost and core performance aspects related to heavy reflector gains, fuel-reflector substitution, and disposal cost policy in the U.S. are examined.

Development of a MELCOR Model for LVR-15 Severe Accidents Assessment

LVR-15 is a light-water-tank-type research reactor placed in a stainless-steel vessel under a shielding cover located in the Research Centre Rez (CVR) near Prague. It is operated at a steady-state power of up to 10 MWt under atmospheric pressure and is cooled by forced circulation. In 2011, the fuel was replaced, going from high-enriched uranium (HEU) to low-enriched uranium (LEU). After 2017, the State Office for Nuclear Safety (SUJB) asked CVR to evaluate the LVR-15 under Design Extended Conditions B (DEC-B). For this reason, a new model was developed in the MELCOR code, which allows for modelling the progression of a severe accident (SA) in light-water nuclear power plants and estimating the behaviour of the reactor under SA conditions. The model was built by collecting information about the LVR-15. Since the research reactor can have different core configurations according to the location of the core components, the core configuration with the most fuel (hottest campaign K221) was selected. Then, to create the radial nodalisation, the details of the core components were obtained and grouped in five radial rings and 27 axial levels. The simulation was run with the boundary conditions collected from campaign K221, and the results were compared with the reference values of the campaign with a negligible percentage of error. For the coolant inlet and outlet temperature, the reference values were 318.18 K and 323.5 K, respectively, while for the simulation, the steady state reached 319 K for the inlet temperature and 324 K for the outlet temperature. Additionally, the cladding temperature of the hottest assembly was compared with the reference value (353.72 K) and the steady-state simulation results (362 K). In future work, different transients leading to severe accidents will be simulated. When simulating the LVR-15 reactor with MELCOR, specific attention is required for the aluminium-cladded fuel assemblies, as the model requires some assumptions to cope with the phenomenological limitations.

Long-term simulation of crystallization fouling in a forced circulation crystallizer

Most heat exchangers in wastewater treatment systems and the thermal desalination industry experience the deposition of unwanted materials on their surfaces. One of the primary causes is the supersaturation of salts with inverse solubility near the heat exchanger's heated surfaces. In this paper, a long-term simulation of the crystallization fouling of calcium carbonate by developing an efficient solver in the OpenFOAM software is proposed. The k-ω SST model was used to simulate turbulence, and the level-set model was adopted for high-precision and high-quality capturing of the fouling front inside the heat transfer tubes of a forced circulation crystallizer. The results demonstrated that the developed solver is a promising tool for accurately predicting moving boundary conjugate heat transfer. Upon validation of the results, the dynamic evolution of the fouling front and its sophisticated interactions with hydrodynamics were examined. The crystallization fouling was found to be under reaction control. Furthermore, the relatively slight supersaturation caused delayed front growth, which prolonged the fouling time to several months. Besides, findings demonstrated that the intensive competition between removal and deposition mechanisms at higher inlet velocities resulted in decreased asymptotic thermal resistance. Additionally, the velocity increase had a smaller impact on reducing the deposit's asymptotic resistance.

Impact of corrugated duct and heat storage element on the performance of a low-cost solar air heater under forced air circulation: an experimental study.

The need to address global warming issues and international policies has placed a greater emphasis on the development of solar energy utilization systems. Intensive study is necessary to expand solar energy applications, as solar energy potential varies widely. This study investigates the thermal and thermohydraulic performance of a modified flat plate solar air heater (FSAH) to assess the effects of using corrugated aluminium duct and sand heat storage elements (HSE) in various combinations. The different arrangements selected for the experimental investigation are the FSAH, FSAH with corrugated aluminium duct (FSAH-C), FSAH with a sand heat storage element (FSAH-S), and FSAH with a combined use of corrugated aluminium duct and a sand heat storage element (FSAH-CS). The materials used for fabrication are low-cost and readily available in the study area. The results indicate that the sand bed enhanced the thermal performance by acting as the thermal heat storage medium, which could also supply heat for a short duration after non-sunny hours, and the corrugated aluminium duct enhanced the surface area and allowed the air to pass twice inside the SAH. We observed that the SAHs with sensible heat storage had a higher top loss compared to the FSAH-S configuration. The average thermal efficiency of the FSAH-CS configuration was 59.17%, which is 8.81%, 5.72%, and 10.95% higher than FSAH-S, FSAH-C, and FSAH, respectively. Furthermore, this configuration achieved an exit temperature of 64.5°C. The proposed system has a thermohydraulic efficiency of 59.14%, which is not significantly different from the average thermal efficiency. Therefore, the suggested system verifies its ability to function without requiring substantial external power.

Influence of Drying Parameters and Methods of Fractionation in the Chemical Composition of Dehydrated Ginger (<i>Zingiber Officinale</i> Roscoe)

Ginger is widely commercialized in the food, chemical, and pharmaceutical industries, mainly in dehydrated and powdered form. To do this, the raw material must go through a drying process, which can significantly influence its characteristics. This study proposed to investigate the ginger dehydration process under three different fractionation methods: whole, sliced, and grated, and subjected to three other drying processes: oven with forced air circulation and renewal (CC) and without forced air circulation and regeneration (SC), both for temperatures of 50, 60, 70 and 80 °C, and freeze-drying. The data obtained allowed the construction of drying curves depending on time. The samples were analyzed for color, phenolic compounds, substances reactive to thiobarbituric acid (TBARS), acidity titratable capacity, 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, and chemical composition of the oils essential, obtained by hydrodistillation. The ginger drying kinetics shows that the process efficiency is maximized by combining parameters such as more significant sample fractionation, high temperatures, and forced air circulation. Notably, the preservation of bioactive compounds is more effective under conditions of lower temperature, lower fractionation, and absence of forced air circulation, highlighting the importance of these factors in maintaining the nutritional properties of ginger. The evaluation of the essential oil reinforces the need for appropriate strategies, such as freeze-drying or drying in an oven with forced air circulation at 50 °C, to minimize the degradation of volatile components, contributing to optimizing ginger dehydration processes promoting and preserving its nutritional and functional benefits.

Intensification of thermal characteristics of flat plate solar water heater using triangular perforated wavy tape

The efficiency of the flat Plate Solar water heater has improved experimentally using passive methods. Experiments have shown that the addition of wavy tape (WT), 6 mm perforated wavy tape (PWT), and 9 mm perforated wavy tape (PWT) to a forced circulation solar water heater improves rate of heat transfer (Nu), friction factor (f), and effectiveness. Wavy tape inside the pipes induces secondary swirl flow, which improves mixing and increases heat transfer coefficients. The heat transfer rate (Nu) is increased by the incorporation of wavy tape; FPC with 6 PWT was higher than FPC without WT, FPC with plain WT, and FPC with 9 PWT by 20.83%, 14.85% and 6.25%, respectively. The maximum temperature difference of FPC with 6 PWT was higher than FPC without WT, FPC with plain WT, and FPC with 9 PWT by 61.9%, 22.9%, and 12.62% respectively. The maximum efficiencies value observed was 37.55%, 49.46%, 54.013%, and 51.03% for FPC without WT, FPC with plain WT, FPC with 6 PWT, and FPC with 9 PWT, respectively.

Implementation of Solar Salt Properties Into ARIANT and Simulation of Pressurized Loss of Forced Circulation in a High Temperature Gas-Cooled Small Modular Reactor

Abstract Small modular reactors (SMRs) are actively being considered for use in Canada. Some proposed SMRs can make use of solar salt as an intermediate coolant for a heat storage system. The development of thermalhydraulic simulation tools is one of the key capabilities needed to examine the performance of SMRs and license this class of reactors. This article summarizes the implementation of molten solar salt fluid properties into the algorithm for analysis of network thermalhydraulics (ARIANT) and uses this code to simulate a high temperature gas-cooled SMR with helium and solar salt as its primary and secondary coolants during a pressurized loss of forced circulation (PLOFC) event. This work demonstrates the ability of ARIANT to simulate transient events in a two-loop reactor system consisting of helium and solar salt as coolants and helps to establish ARIANT as a tool for SMR analysis.

LITEC: An experimental facility for the validation of the IFMIF-DONES Impurity Control System

The Impurity Control System (ICS) of IFMIF-DONES is devoted to assuring lithium purity. After its circulation through the target, some undesired products will contaminate the lithium: deuterium, hydrogen, tritium, and beryllium. In addition, due to the high velocity of the flowing lithium, the target assembly, piping system, and other auxiliaries are subjected to a significant corrosion rate, thus leading also to the presence of metallic impurities in the liquid lithium (iron, nickel, molybdenum…). Finally, nitrogen, oxygen, and carbon will also be present.These impurities may compromise the operation of the facility: they may enhance the erosion/corrosion effect, shortening the operational life of equipment; they may be activated having an important impact on safety strategy, maintenance, and operational procedures; finally, the erosion caused to the target nozzle may produce fluid perturbations affecting to different aspects: fluid-dynamics, cavitation, and thermo-mechanics.The ICS extracts a fraction of the liquid from the DONES main lithium loop to be purified in dedicated traps, to maintain impurities below permissible levels to achieve the required safety and operational conditions.The validation of the ICS at a relevant circuit size will be performed in a new experimental facility called LITEC (The LIthium TEchnologies CIEMAT loop). It consists of a forced circulation lithium circuit. An electromagnetic pump provides a wide operational range for testing all the purification systems envisioned in the ICS. It has four test sections, where trap prototypes will be installed. An injection system also foresees the possibility of introducing impurities to simulate realistic IFMIF-DONES conditions. Finally, a specific branch will monitor online and offline the impurities.LITEC will contribute significantly to clarifying key aspects of the design and operation of IFMIF-DONES lithium systems and will be a reference facility for research activities in lithium technologies. In this work, its engineering design, operational parameters, and characteristics are presented.

Effect of geometry on the evolution of DLOFC transients in high temperature helium loop

Generation IV high-temperature gas-cooled reactors (HTGR) are designed to exhibit passive safety under all off-normal circumstances. One such scenario, known as depressurized loss of forced circulation (DLOFC), occurs after a break in the inlet/outlet header, allowing helium to leak from the reactor. Upon depressurization, the onset of natural circulation (ONC) can occur causing bulk air ingress leading to the oxidation and degradation of core components. The Transformational Challenge Reactor (TCR) has similar features to those of an HTGR, but the primary difference is the use of a more complex, additively manufactured (AM) fuel geometry. The more compact, additively manufactured, ceramic fuel elements can be conveniently produced with optimally configured channels that suppress the air ingress progress and improve thermofluidic performance. DLOFC and air ingress are experimentally studied in a scaled HTGR flow test setup. The experiments use an AM test element embedded with a distributed temperature sensor as well as a test geometry comprised of spherical pebble bed elements. With the test geometries aligned within a lowercase h-shaped tube flow setup, further data was obtained to improve the understanding of DLOFC. The thermal transient and air ingress data gathered for both test geometries are compared. The results show that the AM part delayed ONC as compared to the pebble bed test piece at higher temperatures. The distributed temperature sensor shows intra-leg circulation at higher temperature tests.

Self-assembled concentric stripes of diamond particles by a pinning-depinning mechanism

We describe the novel mechanism of spontaneous formation of the concentric stripe patterns of microdiamonds via gradual solvent evaporation from a suspension confined in a teardrop well. The self-organized patterns exhibit a series of arcs with regular spacings varying between hundreds of micrometers and millimeters. They result from an interplay between the directional forced circulation of the solvent and a stick-slip movement of its contact line during the gradual drying of the suspension. We reveal the mechanism of the phenomenon and discuss the effects of various parameters on the obtained structures.

Successful Water Quality Improvement Practices of a Campus’s River in Ningbo Based on Water Replenishment and Circulation Since Year 2017

Rivers play a critical role in regional water quality, but from time to time concentration of surface water pollutants can easily exceed both national and local water standards. This study debates the feasibility and effectiveness of utilizing the natural treatment potential of flowing river water by replenishing treated sewage effluent and forced circulating. The research combines field experiments and laboratory analyses to assess the impact of this approach on water quality. Theoretical simulation with one-dimension modeling recommended by China’s national standard of “Code of Practice for Computation on Allowable Permitted Assimilative Capacity of Water Bodies” (GB/T 25173-2010) indicates that the target campus river water’s cycle flowing contributes to the further removal of key pollutants from treated sewage, resulting in the improvement of campus river’s water quality downstream along its forced circulation. NH3-N and CODMn levels of the campus’s river water were notably reduced and met the planning water qualities as expected.

Heat transfer in a channel with internal intensifiers during azeotropic mixture circulation

Today, the use of mixtures as refrigerants and coolants in various energy systems is widespread. The volatility coefficients for the components of a non-azeotropic binary mixture vary significantly. In an azeotropic binary mixture, the volatility coefficients for both components are the same. This paper presents the experimental results on the intensity of heat transfer to an azeotropic alcohol-water mixture during forced circulation in a round heated channel. Experiments are carried out both in a smooth channel and in a channel with a spiral intensifier. The inner diameter of the channel is D = 7.6 mm, the length is 2 m. The intensifier surface has a hydrophobic coating. The experiments are carried out at low (0.03 – 0.04 MPa) pressure in the system, in the range of mass velocities 36 < M < 376 kg/m2s and Reynolds numbers of 360 – 3700. The heat flux density in these experiments is 8000 W/m2. In the single-phase flow of an azeotropic alcohol-water mixture in the channel with a spiral intensifier, the heat transfer coefficient is up to 5–6 times higher than that in a smooth channel. In this case, the higher the mass flow velocity, the greater the excess of the heat transfer coefficient. In the two-phase flow of the mixture in the channel with a spiral intensifier, the heat transfer coefficient is up to 2–3 times higher than that in a smooth channel.

Leaf litter nutrient content reveals benefits to traditional cropping systems in the Amazon

Soil fertility in the Amazon rainforest is very dependent to litter decomposition as a source of organic carbon and nutrients. Thus, land use that promote high litter decomposition might play a positive influence on soil chemical properties. The present study aimed to quantify the nutritional content of litter in anthropized and natural environments in Southern Amazonas. The study was conducted on two properties in the municipality of Canutama, in four areas: native forest, annatto, cupuassu, and guarana. In each area, 10 conical collectors (0.21 m²) were installed at a height of 0.3 m from the ground. The samples collected in each area for each month were dried in a forced circulation oven at 60ºC until reaching constant mass and weighed. Macro- and micronutrient content analyses were performed by sulfuric solubilization (N), nitric perchloric solubilization (Ca, Mg, P, K, Na, S, Cu, Fe, Mn, and Zn) and incineration (B). Variance analysis and comparison of means by Tukey test at the 5% probability level were applied to the data obtained, along with a multivariate analysis. This comparison was carried out by evaluating the overall average of a whole year of litter formation, as well as for formation within each month evaluated. Sulfur (S) was the only macronutrient that did not differ between environments (0.1 and 0.2 g kg-1). Macronutrients and micronutrient contents of litter (N: 16.92; Mg: 1.08; Cu: 16.00; Zn: 31.70; B: 104.40; g kg-1) were significantly highest in the annatto area. Annato also presents higher K (9.92 g kg-1) and P (0.70 g kg-1) contents. The litter of natural forest and guarana are richer in P (0.88 g kg-1) and Ca (g kg-1), respectively. Cupuassu litter showed lower nutritional contents, especially in macronutrients contents (N: 9.04; P: 0.51; K: 0.28; Ca: 0.76; Mg: 0.44; g kg-1). This indicates that traditional Amazonian agroecosystems may positively to improve quality of litter and impact nutrient cycling in soils highly weathered in the region.

Foam‐mat‐dried açaí pulp (Euterpe oleracea Mart)

AbstractDrying, as alternative process, enhances stability, eases transport, and prolongs storage for fruits and fruit pulps. This study focused on producing açaí foam with 2% emulsifier and comparing it to a control (0% emulsifier), following by drying (60 °C) in a forced air circulation oven. Açaí powder with 2% emulsifier exhibited a higher effective diffusion coefficient (5.35 × 10−4 cm2 s−1) than the without emulsifier counter part (1.41 × 10−4 cm2 s−1). The pores formed after pulp aeration with the emulsifying agent led to a higher diffusion coefficient and a shorter drying time. Sorption isotherms at 25 °C and 35 °C displayed favorable fits for both powders (R2>0.9). Açaí powder with emulsifier demonstrated superior solubility (47.93%) and faster rehydration (168 s) compared to the control (19.72%; 324 s). The use of a 2% emulsifying agent resulted in a porous, dried açaí powder with improved flowability and solubility, indicating higher quality.Practical applicationsTraditionally, açai pulp is commercialized as a frozen product, which entails high energy costs and logistical constraints. Foam‐mat drying allows the dehydration of viscous, heat‐sensitive, and high‐sugar foods that cannot be effectively dried through spray drying. It offers a practical application in the food industry, particularly as an ingredient. Powdered fruit pulps, including açai pulp, are widely utilized in ice creams, yogurts, and instant juices. To meet industrial requirements, these powders need to exhibit good solubility, quick rehydration, and stability at room temperature. Through foam‐mat drying, high‐quality powdered açai pulp can be produced with a short drying time. This technology enables the production of stable powders that can be easily rehydrated, opening opportunities for new ingredient development and diverse applications.

Theoretical study of a double-slope solar still with solar air heater condenser

Despite their limited water production and efficiency, double-slope solar stills are an appropriate solution for water scarcity in hot arid regions. Numerous studies have focused on enhancing the effectiveness of double-slope solar stills. In this context, this study introduces a double-slope solar with a solar air heater condenser (DSSS-SAHC). The back cover of a conventional double-slope solar still was replaced by a glass air heater in order to recover the still’s thermal losses in heating air. The transient performance of the DSSS-SAHC was investigated numerically under real weather conditions and compared to the performance of a conventional double-slope solar still (CDSSS) with the same aspects. The impact of various weather and operation factors on the DSSS-SAHC performance was investigated at air flows of 0.01 and 0.1 kg/s to account for both natural and forced air circulation, respectively. The results revealed an increase of about 15% and 6% in the thermal efficiency of the DSSS-SAHC over that of the CDSSS, respectively, at air flows of 0.1 and 0.01 kg/s despite the DSSS-SAHC distillate was insignificantly greater than that of the CDSSS at both air flows. In addition, the water distillate of the DSSS-SAHC increased as the solar irradiance increased, the ambient wind and ambient temperature had contrary effects on the efficiency, and the initial saline water level had a negligible impact on the overall performance

Investigation of the thermal performance and environmental impact of a forced circulation solar water heating system during the heating season

A thermal analysis of a forced circulation solar water heating system (SWHS) was carried out. Three different models were analyzed: SWHS without an auxiliary heater, SWHS with an auxiliary heater, and electric heater only. The study was carried out for the province of Mersin-Turkiye. Flat plate collectors with different structural properties were used in simulations, the best results were obtained with the collector with black chrome absorber coating. This system met 55% of the hot water requirement on the design day without requiring any auxiliary heater. During the season, 18.7% of hot water needs were met in January, 20.42% in February, 37.6% in March, 31.2% in November, and 20.5% in December. SWHS with an auxiliary heater, consumed 1130.3 kWh of electrical energy during the heating season, resulting in 540.3 kg of CO2 emissions. 33 % reduction in greenhouse gas (GHG) emissions is achieved with this system compared to a base system powered by electricity only. The hot water use profile is an essential factor in the design of the SWHS. Since the systems using fossil fuels can meet the needs of the users, energy storage techniques must be adapted to the SWHS to be an alternative.

The Passive Heat Removal Facility: Testing and Demonstrating an Innovative Decay Heat Removal System

Innovative reactor concepts are being studied by several research institutions and private entities for their role against climate change and energy poverty. The Generation IV International Forum, committed for more than 20 years in support of advanced reactors, has drawn up a series of objectives for the new class of nuclear plants, among which is an improvement in safety and economy through passive safety systems for the removal of decay heat. One of the most studied technologies is the lead fast reactor (LFR), whose coolant has a high boiling point, excellent shielding capabilities, and good heat transfer in forced and natural circulation, as well as neutron properties suitable for a hard spectrum. These allow for designing systems with high simplification and wide safety margins. On the other hand, opacity, corrosion, and innovative design choices require demonstration of the technology in experimental campaigns before using it in the industrial field. In recent years, Westinghouse Electric Company has begun the conceptual study of an intermediate size LFR [~460 MW(electric)] which, by exploiting the opportunities of the technology, aims at marketability over the next decade. One of the features is a passive heat removal system that allows, through different heat exchange mechanisms including conduction, convection, and radiation, for the transfer of decay heat from the reactor block to a pool of water inside the containment. The system is designed for indefinite heat removal thanks to channels that allow outside air to replace water following complete boiling. For the geometry of the system, the size, the materials, and the heat transfer mechanisms, an experimental activity is required to validate the prediction of the calculation codes and potentially support design optimization. The UK Department for Business, Energy & Industrial Strategy has recently subsidized the design, procurement, installation, and operation of the Passive Heat Removal Facility, an experimental facility to study the innovative safety system. This paper presents the activities of scaling, design, pretesting, and installation of that facility.

Thermal performance of three concentrating collectors with bifacial photovoltaic cells part I – Experimental and computational fluid dynamics study

Bifacial photovoltaic cells can produce electricity from incoming solar radiation on both sides. These cells have a strong potential to reduce electricity generation costs and may play an important role in the energy system of the future. However, today, these cells are mostly deployed with one side receiving only ground reflection, which leads to a profound sub-optimal utilization of one of the sides of the bifacial cells. Concentration allows a better usage of the potential of bifacial cells, which can lead to a lower cost per kWh. However, concentration also adds complexity due to the higher temperatures reached which add the requirement of cooling in order to achieve higher outputs. This way, this paper focuses on the effectiveness of forced air circulation methods by comparing the thermal performance of three specific concentrating bi-facial collector designs. This paper developed a computational model, using ANSYS Fluent intending to assess the thermal performance of a covered concentrating collector with bifacial Photovoltaic (PV) cells. These results have then been validated by outdoor measurements. Results show that even a simple natural ventilation mechanism such as removing the side gable can effectively reduce the receiver temperature, thus resulting in favourable cell operation conditions when compared to the case of an airtight collector. Therefore, compared with a standard model, a decrease of 13.5% on the cell operating temperature was reported when the side gables are removed. However, when forced ventilation is apllied a 22.8% reduction on temperature is found compared to the standard air-tight model. The validated CFD model has proven to be a useful and robust tool for the thermal analysis of solar concentrating systems.